The present invention relates to an electrophotographic apparatus for forming a color-combination image with a plurality of single-color toner images being formed on a photosensitive device and once transferred onto an intermediate transfer device, and more particularly to such an electrophotographic apparatus which controls the image-formation start timings on the photosensitive device.
As one of color-image formation apparatus based on the electrophotographic process technique, there is known an electrophotographic apparatus which is arranged such that a plurality of different-color exposure beams are selectively directed to a photosensitive device to be imaged thereon so as to form a plurality of electrostatic latent images, and the plurality of formed electrostatic latent images are developed with toners having a plurality of different colors so as to form a plurality of toner images which are in turn overlapped with each other to form a color image on a copy sheet. For example, in U.S. Pat. No. 4,652,115 or the Japanese Patent Provisional Publication No. 63-292156, there is disclosed a system in which an intermediate transfer device is placed between a photosensitive device and a copy-sheet carrying device and a plurality of single-color toner images having different colors are successively overlapped and transferred on the intermediate transfer device so as to obtain a combined color image which is in turn transferred onto a copy sheet. Here, for overlapping the plurality of toner images on the intermediate transfer device, various attempts are made for preventing the deterioration of the image due to the dislocation in overlapping between the plurality of toner images. However, such conventional electrophotographic apparatus makes difficult the fine alignment between the photosensitive device and the intermediate transfer device at every color, requires a complicated mechanism such as a clutch mechanism for the positional adjustment between the photosensitive device and the intermediate transfer device and provides the possibility that the photosensitive device and the intermediate transfer device are damaged in the positional adjustment, as will hereinafter be described in detail.